---
title: Self-hosted migrations
description: Plan and apply database migrations for a self-hosted c15t backend
  with the c15t CLI self-host migrate command.
group: cli
lastModified: "2026-10-10T16:01:45+01:00"
---
## Plan a migration

```bash
npx @c15t/cli@alpha self-host migrate --config ./c15t-backend.config.ts --plan --json
```

The CLI reads the `database` option from the config file, loading `.env` from
the file's directory, and reports what it would change. `--plan` changes no
schema. Without `--config`, the CLI looks for `c15t-backend.config.ts`; in a
terminal it can help you create one.

A v2 config that only has `adapter` fails with a message naming the field.
Replace it with `database`, as the
[database setup guide](/docs/self-host/guides/database-setup#upgrade-a-v2-backend)
shows.

## Apply it

```bash
npx @c15t/cli@alpha self-host migrate --config ./c15t-backend.config.ts --apply --json
```

`--apply` is the only flag that writes. Without `--plan` or `--apply`, a
terminal shows the plan and asks before applying; a script must pass one of
them. `--json` alone never applies a migration.

The result reports planned, applied, already current or cancelled work. A
database the migrator does not recognize fails with an explanation instead of
being changed. The CLI closes its database connection when it finishes, also on
failure.

Back up the database before applying against existing data, and run the
migration against the same database and schema the server uses. Codemods do
not migrate a database.